Test 3 - Influenza Flashcards
Influenza is an ___(a)___ virus, meaning that it _____(b)_____.
(a) enveloped
(b) merges with hoest membrane
What is the purpose of HA? Of NA?
HA (Haemaglutinin): Viral envelop protein that binds to host sialic acid receptor to trigger endocytosis.
NA (Neuraminidase): Allows virus to “bud out” of host, causes inflammation and cell/host death in turn.
Virulence depends highly on…
Rate of intracellular replication.
H5N1 Influenza is also known as ______. It (is/isn’t) fatal.
Avian flu; is fatal.
What are the three types of Influenza? Defining Characteristics of each?
- Influenza A: Wide host range, causes pandemics.
- Influenza B: Limited host range, most common flu.
- Influenza C: Single HA-NA fusion protein, only mild flu.
The surface protein of Influenza A are…
- HA
- NA
- M2
M2 is a…
tetramer ion channel on surface of Influenza A
The genome of Influenza A is made up of …
(-) RNA strands
The genetic material of Influenza A exists as a (1) after it is complexed with (2), which _____ and (3), which includes (give the 3 examples).
- Ribonucleoprotein
- Nucelocapsid (NP) protein, which stabilize the genome
- Viral RNA polymerase (PB1, PB2, PA)
The lipid bilayer of the influenza virus is…
from the host and includes host receptors.
Similarities between HIV and Influenza includes (2)…
- Both RNA virus
2. Both approx. same size
The differences between HIV and Influenza includes (2)…
- HIV has (+) strand RNA, which can act as an mRNA, while Influenza has (-) strand DNA, which can act only as a template and must be replicated by RNA polymerase.
- HIV has just a Reverse Transcriptase, which changes (+) RNA into dsDNA, but Influenza has 3 RNA Polymerase (PB1, PB2, and PA), 3 surface proteins (HA, NA, and M2), NP, and NS1 and NS2, which are splicing proteins.
What specific part of human host receptor does HA attach to? How is this process different in different strains of Influenza?
HA attaches to Sialic Acid, 6-C sugar moeity of receptor. Different HA strains recognize different Sialic Acid regions.
HA is a…
trimer fusion protein with 3 N-terminals.
After HA binds to host, what happens? (4)
- Cell-mediated Endocytosis
- Lysosome engulfs virion (– pH)
- –pH causes HA to undergo conformational shift, exposing a hydrophobic side and causing the virion to stick to endosome.
- H+ enters virion through M2 channel, launching membrane fusion and eventual “dumping” of the genetic material.
After viral genome is dumped into cytosol, what happens?
- (-) Strand RNA and Polymerase then migrate into nucleus.
- Viral RNA polymerase replicate RNA into (+) Strands.
- (+) RNA capped by splicing with 5’-capped host RNA fragments.
- (+) RNA with 5’ cap act like normal mRNA and is translated by host ribosome.
Why does the virus steal 5’ Cap to create a chimera?
“Naked” RNA without poly-A 5’ tail is hydrolyzed by host mechanism.
What is Antigenic Drift? Why is it advantageous?
In a s single infection, antigen of infectant to change due to random mutation. This may allow the virus to outpace the host’s ability to create T cells.
What is Antigenic Shift? Example?
Reassortment of viral genetics from cross-species (multiple) infectivity. For example, Avian HA may undergo antigenic drift to infect mammals as well as avians.
What is a zoonotic virus?
Virus acting across species.
How may an avian virus undergo Antigenic Shift?
- Zoonotic avian virus infects pig.
- Pig also has swine flu.
- During replication within host cell, avian flu RNA and swine flu RNA fragments may be in some cytosol, and chromosomes may be reasserted.
Why is Antigenic Shift particularly dangerous?
If HA is from swine flu and NA is from avian flu, it is harder to develop antibody against because NA (surface protein as well as “budding” protein) is completely foreign.
Avian Flu is also known as…
H5N1
Yoshihiro Kawaoka: Began with …
H5N1 Avian Flu.
